The world's largest staffing company said its revenues increased by just 2 percent in July and August, and at an even slower rate during September, sending its stock sharply lower.

"When we came out of the holiday period and entered September we didn't see the growth coming back we had in Q2," Ploos van Amstel said in a telephone interview.

"Part of the deceleration is related to the market slowdown in France as well a slowdown on the back of high double-digit growth rates in Italy and Spain."

Germany, where the company has been integrating the Tuja and Adecco brands, had also been difficult, he said.

The deceleration could be due to orders being pulled forward into the second quarter rather than concerns over a possible trade war, the executive said, although Adecco would examine the reasons in the coming weeks.

The company kept its goal of increasing revenue at four times the rate of global GDP growth in the mid-term, Ploos van Amstel said, by winning market share from local rivals.

"That is still the goal, we want to capture a higher share of the economy. Although the performance so far this quarter hasn't been good, the digital initiatives we have to transform the business are very exciting.

"With technology we can make the investments that local competitors cannot make, and we can reduce fragmentation in the industry." (Reporting by John Revill; Editing by Michael Shields)